1. Field of the Invention
The present invention relates to the field of methods for inspecting the printing state of materials printed on substrates, and substrates to be printed
2. Description of the Prior Art
In the manufacturing process of circuit substrates (hereinafter referred to as xe2x80x9csubstratesxe2x80x9d) on which electronic components are mounted, the mounting state is inspected to secure the reliability of each product. Normally, an appearance inspection is implemented using a camera for examining the soldering state of electronic components mounted on a substrate. CSPs (chip size packages) and BGAs (ball grid arrays) are bonded onto the substrate using bumps provided on the bottom face of electronic components. The normal appearance inspection method involves observing the upper face of the substrate, and thus is not effective for inspecting the mounting state of these types of components because the soldered portion is concealed by the electronic component itself after being mounted. Accordingly, the printing state of solder paste (hereafter referred to as xe2x80x9csolderxe2x80x9d) on the substrate is inspected, instead of the appearance inspection, to ensure reliability.
In order to improve the reliability of the inspection itself, all printed points on the substrate should ideally be inspected in the above inspection of the printing state. However, inspection of all printed points would require a long time because the camera would need to move to each target portion to check and evaluate the printing state by visual recognition. This reduces productivity, and increases equipment costs, since an exclusive inspection apparatus would be needed.
The present invention aims to provide a method for inspecting the solder printing state at low cost while securing the necessary degree of accuracy.
The inspection method of the present invention is to inspect materials printed in a predetermined pattern on a substrate by detecting the printed state with a detection means.
In the present invention, a test printing portion having a pattern dimension smaller than a minimum printing pattern dimension of an actual pattern to be printed is provided on the substrate. After printing, the test printing portion is detected by the detection means for examining the printing state. According to the inspection results of the test printing portion, the printing state of the entire substrate is judged. The test printing portion is provided on a periphery of the substrate outside of the effective printing region, or a space region inside the effective printing region. The detection means detects the printing state of the test printing portion, and the printing state of the entire substrate is judged based on the inspection results. Accordingly, the present invention enables the printing state to be inspected at low cost while securing the necessary degree of accuracy.